Reports that sphingosine 1-phosphate was a ligand of GPR12 [4,11] were not reproduced in later studies using the β-arrestin PathHunter assay [9,12]. Tyrosol has been proposed to be a possible ligand for GPR12 [5].

Higher expresssion of GPR12 was detected in areas of neuronal differentiation, whereas GPR12 transcritpts were not detected in the regions of neuroblast proliferation [4]. GPR12 protein expression was upregulated in human vascular endothelial cells exposed to fluid shear stress, despite that there was no increase of GPR12 expression in the mRNA level [11]. GPR12 RNA was not detected in human oocytes examined by RT-PCR [2].